1. Field of the Invention
The present invention relates to a latching mechanism, and more particularly, to a latching mechanism that resists corrosion, simplifies routine maintenance, among other benefits.
2. Background of the Invention
Latching mechanisms used in shipboard marine applications must withstand extremely corrosive environments while maintaining watertight mechanical seals. In applications such as weatherproof deck doors, windows, hatches, and scuttles, watertight door latches (also known as dog latches) must provide a strong mechanical seal, must be operational through a wide range of temperature extremes, and must prevent the passage of water and air in heating ventilation and cooling systems. In addition, the latches must operate quickly to permit rapid opening and closing during a fire or other emergency situation.
FIGS. 1A and 1B illustrate a typical prior art latching mechanism. The main components include a sleeve, a spindle rotating within the sleeve, and a spring, string packing, and bushings positioned in the annular space between the sleeve and spindle. In some cases, the spindle has a channel through which lubricant is added. A dog lever is attached at one end of the spindle for actuating the spindle, while a dog latch is attached at the other end for engaging a door or other object. Manually pushing and turning the dog lever rotates the dog latch and either engages or releases a door or other object against an adjoining bulkhead or frame. Optionally, a suitable electromechanical actuator can operate the lever remotely and/or automatically. Another example of a conventional mechanism is disclosed in U.S. Pat. No. 4,403,779, hereby incorporated by reference.
Although the prior art latching mechanisms enable lubrication of the components within the sleeve, the components are typically non-porous, resulting in a lubrication that merely coats the bearing surfaces and is easily worn away. Further, the components themselves are typically constructed of dissimilar metals and suffer from corrosion. Thus, even with careful maintenance and periodic relubrication, the useful life of a prior art mechanism is limited by internal wear and corrosion.
Thus, there remains a need for a latching mechanism that separates the dissimilar metals of the components within the sleeve and uses materials that absorb lubricant to provide constant protection against wear.
The present invention is a latching mechanism that reduces wear and corrosion by using lubricant impregnated components and minimizes contact between dissimilar metals. Instead of the bushings known in the prior art, the present invention uses bearings impregnated with materials that enhance corrosion and wear protection in the annular space between the spindle and sleeve. These porous bearings absorb lubricant and provide a constant protective lubricant layer between the spindle and bearing surfaces. Further, through the use of corrosion resistant impregnating oils the effect of dissimilar metals corrosion is diminished.
In addition to the lubricant in the bearing material, the present invention provides means for adding lubricant through the spindle. Using a commercially available grease fitting, such as a zerk fitting or an Allemite(trademark) fitting, lubricant is added at the distal end of the spindle. The lubricant passes through channels in the spindle, and fills the annular space between the sleeve and spindle. By eliminating voids and providing lubrication under pressure, the components of the latch are more effectively isolated, e.g., reducing the onset and affects of crevice corrosion. Sealed by the lubricant, the latching mechanism is pressure tight, e.g., to greater than 15 psi, and corrosion resistant without adversely impacting rotational torque.
Accordingly, an object of the present invention is to provide a latching mechanism that resists corrosion and wear while providing a tight mechanical seal.
It is another object of the present invention to maintain internal lubrication with minimal maintenance and addition of lubricant.